Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 171158
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
558 AM CST Sun Dec 17 2017

.UPDATE...
Updated for 12Z aviation discussion

&&

.AVIATION...
12Z TAF discussion:
Aviation weather will be poor for most of this forecast period
from today through tonight. Widespread RA/SHRA will be moving
across the forecast area this morning before exiting to the east
by early afternoon. MVFR to IFR ceilings will accompany the rain,
but expect ceilings to lower further to potentially LIFR category
when the rain ends, especially along/east of the GWO to HKS/JAN
corridor. Fog is looking more likely as well tonight along the
GTR/MEI/HBG corridor due to little mixing of the moist airmass
following this system combined with the relatively cold ground.
/EC/

&&

.DISCUSSION...

As anticipated, a large area of rain and embedded thunderstorms
is moving across the ArkLaMiss early this morning in association
with a quick-moving shortwave trough. Anomalous precipitable water
in excess of 1.5 inches is supporting heavy downpours, and at
least a few locations will receive over an inch of rainfall in
spite of the progressive nature of the system. Guidance has sped
up some with the exit of the better large scale ascent by this
afternoon, and have adjusted the forecast accordingly. However,
expect periods of rainfall to be possible from later tonight into
Monday as moisture convergence and subtle perturbations in the
large scale flow help to reinitiate shower/tstm activity,
especially for locations along/south of the I-20 corridor.
Otherwise, milder temperatures can be expected, especially tonight
when lows should be near 15 degrees above normal. /EC/

An active late December weather pattern will continue to divulge
through the mid and long term portions of the forecast. This next
seven days could be the wettest we`ve experienced in quite some time
in the ArkLaMiss. WPC 7 day QPF totals are in excess of 6" in
portions of the Delta and range from 2" upwards elsewhere. If this
forecast holds true, it will undoubtedly put a significant dent in
our current drought and help erase some of the yearly rainfall
deficits at some sites and add to the surplus at others before the
year ends.

A very moist airmass will exist over the ArkLaMiss on Monday through
Tuesday as the persistent upper level SW flow pattern and low level
southerly flow result in Pwats near their climatological maxes.
Significant rain chances will persist through the early week period.
The best chances for storms will exist on Tuesday through early
Wednesday as a surface front that is associated with a closed upper
low that will begin to cross the southern Plains and approach our
region, swings through the region. Southerly flow will increase
ahead of this frontal passage and the GFS is pretty aggressive with
atmospheric destabilization ahead of the front, depicting CAPE
values ranging from 400-1200 j/kg Tuesday afternoon through
Wednesday morning. A few strong storms could be possible during this
period but it will depend heavily on clearing ahead of and the
timing of the frontal passage. Drier air will begin to filter into
the region by late Wednesday after the front has swept through the
area. Another, deeper, cutoff low will approach the region later in
the work week, pushing another front through the region, which
will once again lead to increased rainfall chances on Friday into
Saturday.

Although model similitude begins to decrease as we get closer to the
weekend, they have come into better agreement than previous runs, as
they continue to depict a weather situation over the holiday period
that definitely warrants cognizance. Confidence is still too low to
mention any solutions just yet, but hopefully we will be able to
better gauge solutions or possible impacts in subsequent
forecasts. /JPM3/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       65  50  65  58 /  99  22  52  42
Meridian      57  48  62  55 /  98  35  43  41
Vicksburg     64  50  66  58 /  94  20  58  55
Hattiesburg   63  56  66  59 /  99  42  66  41
Natchez       66  54  66  60 /  96  35  68  42
Greenville    57  44  62  55 /  79   6  12  57
Greenwood     58  46  64  54 / 100   7  15  53

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.

&&


$$


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